Artavasdes I, king of Media Atropatene, is the ally of the Parthian king Phraates IV when Antony leads his campaign against Parthia in 36 BCE,

Antony leads his troops from Zeugma northward into Armenia and then invades the domain of Artavasdes I. Antony does not want to attack Parthia from the west, which is the shortest way, but—surprisingly—from the north.

Antony allegedly uses this strategy on the advice of Artavasdes II of Armenia, the enemy of Artavasdes I.

Antony moves with his army in fast marches to Phraaspa (possibly Zahhak Castle) , the strongest fortress in Media Atropatene, where Artavasdes I has gotten his family to safety.

Artavasdes I has meanwhile joined the army of Phraates IV.

Antony is not able to take Phraaspa and besieges the city, but Artavasdes I and the Parthian commander Monaeses destroy two legions of Antony's general, Oppius Statianus, who had slowly followed with the siege machines of Antony's troops.

As Antony cannot capture Phraaspa without these machines, he is forced to withdraw and Parthia is not invaded.

Antony, again with Egyptian money, and believing himself betrayed by Artavasdes II of Armenia, has concluded a treaty of alliance with Artavasdes I of Media Atropatene, who had maintained his ground against the Romans but his domain had been severely ravaged.

In addition, his stronger ally Phraates IV had treated him with condescension and given him very little booty.

To deepen this friendship Alexander Helios, the son of Antony and Cleopatra VII of Egypt, is betrothed in 34 BCE to Artavasdes’ daughter Iotapa, although both are infants.

Antony now invades the Armenian kingdom and takes Artavasdes II prisoner.